William foster and egbert foster



W & R. POSTER. TAP FOR CUTTING SCREWS.

Patented Dec. 20

WILLIA'M FOSTER AND ROBERT FOSTER, orivnw Ydiztt,

SCREW-TAP.

Specification of Letters Patent No. 26,487, dated December 20,

To all whom it may concern:

Be it known that we, WILLIAM FOSTER and ROBERT FOSTER, both of the city, county, and State of New York, have invented a new and Improved Tap for Cutting Screws; and We do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the annexed drawings, making a part of this specification, in which- Figure 1, is an external view of our invention. Fig. 2, is a side sectional view of i the same. Fig. 3, is an inverted plan of the same.

Similar letters of reference indicate correspondin parts in the several figures.

Theo ject of this invention is to expedite the withdrawal of the tap from its work after the latter has been performed, so as to save the time hitherto lost by the slow reverse withdrawal movement of the tap in the screw cut by it, and consequently obviate the necessity for the reversing gear hitherto necessarily employed in order to withdraw the tap. i

To enable those skilled in the art to fully understand and constructour inventionwe will proceed to describe it. h

A, is the stock of the tap which is formed of a cylindrical portion a, and a conical portion 6, the former being attached to a rotating arbor c. The stock is formed of steel and on the cylindrical portion a, thereof a collar B, is fitted and allowed to turn freely, said collar being provided with a handle d, at two opposite points of its periphery. The collar B, is provided with two oblique slots 6, e, which have reverse positions relatively with each other and in which the ends of a pin f, fit, said pin passing transversely through the cylindrical part a, of the stock.

In the conical portion 6, as well as in the cylindrical portion a, of the stock A, grooves g, are made longitudinally and at equal distances apart. These grooves have inclined backs k, as shown clearly in Fig. 2, and each groove has a lateral recess 2', at each side of it and extending its whole length. In the grooves b, cutters C, areplaced and allowed to slide freely. These cutters C, are formed of steel bars having their back edges made oblique or taper corresponding to the incli nation of the backs of the grooves g, and each bar has a lateral projecting strip 7', at each side which strips fit in the recesses i, of

clearly in Fig. 3. The outerxsurface of each 1 bar is cut transversely formingjthe; section of a screw, as shownat is, andcorresponding i 60. if

to the thread of the female screw to be out,

the grooves g, and formi f dovetail, h n I one edge of eachbarwbeinga littlemore prominent thanthe other in. order toform cutters. The parts of the bars overl which 1 the collar B, works are smooth. asushownfatz a I Z, and each smooth partlfisi providedwwith a projection m, which fitsintoa groove n, 1 in the inner side Ofvtli. collar B, asshownin Fig. 2. i

The operation isiasi followsz The arbor i is rotated from left to right and' the tap is applied to its work as usual, see Figs. land i 2, the cutters C as they rotate inthehole 1 I cutting the screw, thecutters feeding; them-1; selves to their work precisely the same. as. 1 those of an ordinary tap... When the tap is at work, the cutters 0, have their outer ends 1 flush with the end of the conical, part b, of 1 the stock and the zcuttingparts R, of the cutters project suificientlyafrom the conical ,j]

portion 1), of the headyso that tliey n ay perform their work. wWhenthe work is loom 1 pleted, that is to say,..the screw cut, the operator or attendant grasps 10n e.QI' bOthOf 1 the handles d, of .thecollar B, and arrests its rotation and the arbor i, istill vmovingf will cause the cutters C, to beflforcedout ward, as shown in Fig.2, and owingltoqt inclined backsjh, oflthegroovesg, aII ClL C O responding form of the backs: of the cutters,

the latter will be drawn. inward toward each other as they are forced outwardandj the cutters will consequently be free,jfrom,their work, that is, the screw cutlby them, "andthe tap may be immediately withdrawn. j 1 1;.

Taps constructed inthe usualway require, each time a screw isicut,toflhave;their motion reversed in order that; they may ibe withq drawn from them. Thewithdrawal there-Q required to cuttheflscrews, .and itflalso inf fore of'the taps consumes as muchtime asis volves the necessity oftareversing gearcon-g j nected with the arbor so that its motion may. 1 :I be reversed to effect the withdrawalofflthef tap. By our inventionthis reversin gear; u 1

is dispensed with and the direct; attac inent. 1

of a weight to thearbor isipermitted sca ar:

the tap may be automatically}withdrawnras soon as the cutters C, arereleasedlfrom their} i work. i l Having thus described our} nvention, we

claim as new and desire to secure by Letters Patent The combination of the oblique backed taps C, and slotted collar B, With the taper- 5 ing or conical stock A, substantially as shown and described, so that on turning the collar the cutting threads of the taps will be I released from the nut and thus allow. the

tool to be Withdrawn all as specified.

WILLIAM FOSTER. ROBERT FOSTER.

Witnesses:

THos. BENNETT, J 01m BROUGHTON. 

